Answer:
gullies and stream-like channels
Step-by-step explanation:
Water on Mars exists in the form of ice in polar ice caps and in the form of vapor in a very small quantity in its atmosphere. It is considered that billion of years ago, Mars must have denser atmosphere and its surface would have large amount of liquid water.
NASA mission-Curiosity rover on planet Mars sent back images of its surface providing direct evidence of liquid water on the planet in 2012. The images showed the gullies and stream-like channels where once the liquid water flowed vigorously.